A wide variety of toxins exist in nature and they can also be synthetically produced. They vary in their structural complexity, ranging from formic acid produced by ants to protein toxins produced by several bacteria. Neurotoxins are among the most poisonous and fastest acting toxins. They specifically target the nervous system of animals, including humans, by interfering with the transmission of nervous signals. Neurotoxins are generally more lethal than toxins produced by microbes, and can cause incapacitation or death of the affected individual within minutes of exposure. As a result, neurotoxins have been and will continue to be significant potential candidates for weaponization. Examples of weaponized neurotoxins include Tabun (GA), Sarin (GB), Soman (GD), Cyclosarin (GF), DFP, DMMP, and VX, among others.
Each of these listed neurotoxins, and others, are organophosphates. Their neurotoxic activity arises from their ability to inhibit the functionality of acetylcholine esterase (AChE). Under normal conditions, AChE catalyzes the hydrolysis of the neurotransmitter acetylcholine (ACh) to acetic acid and choline. This reaction allows cholinergic neurons to return to their resting state after activation. In the presence of organophosphates, however, AChE is inhibited and neurons are unable to return to their resting state. In low doses, this results in eye watering and excessive salivation, and in higher doses, individuals are afflicted with various conditions, including salivation, lacrimation, urination, defecation, gastro intestinal upset, and emesis. When dosage is high enough, exposure to these compounds can also result in death. It is these properties of organophosphates that make them particularly suited for use not only as pesticides, but also as potential chemical warfare agents.
Because of this potential use of organophosphates as weapons and the speed with which they attack the human body after exposure, there is a critical need for an efficient method to quickly and accurately detect these highly toxic compounds. While there have been several developments in the past decade for detection of organophosphates, including colorimetric detection methods, surface acoustic wave (SAW) devices, enzymatic assays, and interferometry, each of these has at least one disadvantage. The limitations of these existing methods include slow response time, lack of specificity, low sensitivity, operational complexity or non-portability. For example, two major approaches that have received extensive attention are immuno-based assays and DNA sequencing schemes. However, immuno-based assays are difficult to implement outside of the laboratory because of the instability of the antibodies involved and the necessity of including unstable reagents in the assay. And DNA sequencing techniques are time and instrument-intensive, so therefore they cannot meet the requirements for practical field use. Additionally, both approaches require extensive operator training to be properly implemented.
Another common approach to sensing the presence of organophosphates is to rely upon an immobilized AChE detector coupled to a transducer such as Ph electrodes, fiber optics, and piezo electric crystals. This approach, however, is hampered by several limitations. For example, immobilized enzymes are sensitive and detect a broad spectrum of AChE inhibitors. Because of this broad range sensitivity, they lack selectivity and are prone to false positive alerts, particularly when exposed to choline mimics.
In addition to detection of organophosphates, there is a need for any sensor to convert a detector's chemical, mechanical, or optical change into a measurable signal when the organophosphates are present. Many different types of sensors are known in the art. For example, chemical sensors often detect conductivity changes, amperometric changes, or potentiometric changes. Optical sensors detect changes in emission or absorption. Mechanical sensors can detect changes in mechanical properties or impedance. However, none of the known sensors are or can be linked to a detection sensitive material which provides both quickness of alert and accuracy of detection.
As can be seen from the foregoing, there is a need in the art for development of a way to quickly detect the presence of neurotoxins in such a way that can be utilized in non-laboratory applications, by minimally trained personnel, with a low incidence of false positive alerts.
It is therefore an object of the present invention to provide a neurotoxin-sensitive compound that can selectively detect various organophosphates agents over a range of concentrations and conditions.
A further object of this invention is to provide a compound for use in optoelectronic sensors to detect organophosphates agents.
It is another object of this invention to provide a polymer capable of use in optoelectric sensors for detection of organophosphates agents.
Another object of this invention is to provide a method for detecting organophosphate agents using lumiphoric compounds.
These and other objects of the present invention will become apparent from the description of the invention that follows.